Department of Mechanical and Process Engineering, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland.
Mechanical, Industrial, and Manufacturing Engineering Department, University of Toledo, Toledo, OH, USA.
J Biomech. 2022 Aug;141:111211. doi: 10.1016/j.jbiomech.2022.111211. Epub 2022 Jun 27.
The process of an intracranial aneurysm development, growth, and rupture is multifaceted and complex. In addition, clinical observations have identified the potential of thrombus formation within such aneurysms. While the underlying mechanism is not fully understood, the thrombi represent a potential risk factor for ischemic stroke. Emerging studies indicate that blood residence time (RT) is a promising hemodynamic metric associated with the aneurysm rupture and formation of intra-aneurysmal thrombi. Here, we present a methodology to experimentally evaluate both trajectory-wise and local RT based on magnetic resonance imaging (MRI) velocimetry, and apply it to in vitro flow measurements in scaled-up replicas of 9 patient-specific intracranial aneurysms. Lagrangian tracks of massless tracers are integrated from the velocity fields and averaged to return the mean RT in the aneurysm sac. This is found to be closely approximated by a simple time scale based on the sac diameter and space-time average of the aneurysmal fluid velocity. The mean RT is also correlated with the inflow time scale at the parent artery. These results also provide a basis for the estimation of RT when high-resolution hemodynamic maps are not available. With the continuous increase in accuracy and resolution enabled by progress in MRI technology, the methodology described here may in the future be applicable to in vivo data.
颅内动脉瘤的发展、生长和破裂过程是多方面且复杂的。此外，临床观察已经确定了这些动脉瘤内血栓形成的潜力。尽管其潜在机制尚未完全阐明，但血栓代表了缺血性中风的潜在风险因素。新兴研究表明，血流驻留时间（RT）是与动脉瘤破裂和瘤内血栓形成相关的一种有前途的血流动力学指标。在这里，我们提出了一种基于磁共振成像（MRI）速度测量的实验评估轨迹和局部 RT 的方法，并将其应用于 9 个患者特定颅内动脉瘤放大模型的体外流量测量中。从速度场中整合无质量示踪剂的拉格朗日轨迹，并对其进行平均，以返回动脉瘤囊中平均 RT。结果发现，该平均值可以通过基于囊直径和动脉瘤内流体速度的时空平均值的简单时间尺度来很好地逼近。平均 RT 也与母动脉的流入时间尺度相关。这些结果还为在没有高分辨率血流动力学图谱时估计 RT 提供了依据。随着 MRI 技术进步带来的准确性和分辨率的不断提高，这里描述的方法将来可能适用于体内数据。
